This retrospective-prospective study will identify mother-offspring pairs where prenatal estrogen exposure occurred and will determine the cancer incidence among these mothers and offspring. Two control groups of mother-offspring pairs will be identified and the cancer incidence among these women and their offspring will be compared to that in the at-risk group. One group will be based on physician-matched connrols, the second control group will be selected using Connecticut birth registration data. Cancer experience will be determined through linking the names of members of the cohort to patient reported to the Connecticut Tumor Registry. All cancer sites will be considered with particular attention on reproductive system cancers. To date, more than 800 exposed mother-offspring pairs and 800 physician-matched control pairs have been identified and detailed information has been abstracted from their prenatal records.